1. Field of the Invention
This invention relates generally to bolometer type radiation sensors for detecting thermal radiation and more particularly to the interface circuitry between a silicon type bolometer sensor and the antenna means therefor.
2. Related Art
Bolometers are well known in the art and comprise devices which generate a voltage output when thermal radiation is absorbed. These devices have been successfully used for infra-red (IR) imaging in the long wave infra-red (LWIR) band of the electromagnetic spectrum. Extending these devices to other spectral bands has proven relatively difficult in the past. However, efforts are currently under way to extend this capability to millimeter wave to the (MM) and terrahertz (THz) spectral bands and thus there is a need for imagers operating in the MM and THz spectral bands. Applications for such devices include, for example, multi-spectral imaging for improved navigation, target recognition and detection as well as homeland defense applications. Such applications all require the use of bolometers. Therefore, realizing bolometers with acceptable performance with MM-THZ-LWIR cameras requires the formulation of new approaches for overcoming conventional limitations such as the requirement for faster response time and the ability to maintain sensitivity for relatively long periods A fast response time accordingly dictates minimizing the mass of the bolometer's absorbing element.
In related application Ser. No. 11/240,772 entitled “Sensitive Silicon Sensor and Test Structure For An Ultra-Sensitive Silicon Sensor”, there is disclosed a sensor of thermal radiation comprised of a pair of silicon diodes connected in back-to-back relationship with one of the diodes being located in a detector stage, while the other diode is located in a heat bath stage along with a temperature difference amplifier. The detector stage is thermally isolated from the heat bath stage by a low thermal conductivity link which includes electrical wiring for connecting the back-to-back diodes.
In U.S. Pat. No. 7,157,708 entitled “Ultra-Sensitive Silicon Sensor Readout Circuitry”, there is disclosed circuitry for providing cancellation of local threshold voltage variations and low frequency 1/f noise components in the pixel readout circuitry of an electro-thermal feedback loop including the heat generated by an amplifier circuit located an intermediate stage of a silicon sensor including a detector stage and a heat bath stage.
In U.S. Pat. No. 6,489,615, entitled, “Ultra-Sensitive Silicon Sensor” dated Dec. 3, 2002, there is shown a pair of back-to-back temperature sensing silicon diodes respectively located in a detector stage and an intermediate stage and coupled to a temperature difference amplifier also located in the intermediate stage. The intermediate stage is located between the detector stage and the heat bath stage, with the intermediate stage also including a electro-thermal feedback loop which is provided by the heat generated by an amplifier located in the intermediate stage which generates heat which is proportional to the temperature difference between the difference between the detected temperatures provided by the silicon diodes. The heat provided by the amplifier itself actively minimizes or zeroes the temperature difference between the detector and the intermediate stage so as to minimize or zero any net heat flow between the detector element and the intermediate stage.